During the natural gas production with coal, CO and H2 in the syngas will react in multiple sections of methanator reactors and produce methane. The methanization reaction is a strong exothermic reaction and thus waste heat boiler is to be arranged between two methanator reactors in order to control the syngas temperature. Compared with waste heat boiler in ordinary cases, the methanator waste heat boiler has the following features:
● High inlet/exit pressure (3MPa) and temperature (550～700℃) at the process gas side;
● great variation of load (40~100%), while a constant exit temperature is required at the process gas side, so that a bypass valve has to be provided for control purpose;
● High methane and hydrogen content in the process gas makes it highly corrosive and thus has high requirement for the material;
● Flexible tube sheet is used in order to reduce the weight of the waste heat boiler, which increases the difficulties in welding the heat exchanging .